This invention relates to an optical-type position and posture detecting device, and particularly to a device for detecting a three-dimensional position and a posture of a body. The position and posture of the body can be detected, without contact, by mounting the light receiving element on the body to obtain the spatial movement of the body.
Conventionally, as means for detecting the posture of a body, gyroscope has been usually used. However, the gyroscope is very expensive due to precision of its construction. Furthermore, with a system using a light, a plurality of light sources are disposed at a detected section and a plurality of CCD (or charge coupled device) line sensors are disposed as light receiving elements at a light receiving section, and the posture is obtained from the relation between the plurality of light sources and the plurality of light receiving elements.
As for the optical detection of two-dimensional or three-dimensional position coordinates, the coordinate is calculated on the basis of the principle of triangle measurement by positioning a light source on a body and receiving the light from the light source on a plurality of light receiving elements.
Fundamentally, conventional posture detecting means are bulky in construction or complicated. Consequently, they are expensive or not easily movable, and thus not easily be handled. In the meanwhile, the device for detection of position coordinate are simple in construction. However, it cannot simultaneously detect the posture since the light source is disposed at the side of the body in the optical triangle measurement.
This invention also relates to an angle detecting device.
The angle detecting devices are utilized for detecting the position coordinate (two-dimensional coordinate) of the body (or the light source) or for detecting the angle of rotation of the body (the angle of swing of the body) by combining two angle detecting devices. The angle (or position coordinate or angle of rotation) detected by the angle detecting devices is used, for example, as information inputted to an input device for a computer. There have been proposed various types of such angle detecting devices. For example, as an angle detecting device having a movable portion, there is one in which a cylinder with a slit is rotated, and when the slit is directed to the light source is detected by light receiving element positioned within the cylinder and the angle at that time is detected through the position of the slit. There is another one in which the direction of the light source is traced by changing the angle of the light receiving element with respect to the light source so that the quantity of light received from the light source becomes maximum and the angle is continuously detected from the position indicating at the maximum quantity of light. Furthermore, as an angle detecting device not having a movable portion, for example, there is one in which a PSD or a position sensitive device is provided, a lens is disposed in front of the PSD, a light from a light source is focused by the lens, and an angle of the light source is detected through the position where the light spot impinges on the PSD.
The former angle detecting device is complicated in construction and is liable to cause troubles since it has a movable portion. Furthermore, it usually tares much time for detection. Although the latter angle detecting device does not have the above-mentioned problems, the PSD is relatively expensive and the lens is required.
In order to overcome the above-mentioned problems, it has been proposed that a two-division photodetector (two-division photodiode: for one-dimensional angle detection) or a four-division photodetector (four-division PIN photodiode: for two-dimensional angle detection) are used for detection of angle. The two-division photodetector has two light receiving portions disposed adjacent to each other and each light receiving portion independently, electrically detects the quantity of incident light while the four-division photodetector has four light portions, that is, an upper left portion, an upper right portion, a lower left portion and a lower right portion, and each light receiving portion independently, electrically detects the quantity of incident light. In order to detect the angle, an aperture or an opening is disposed in front of the photodetector and the aperture should be set so that the incident light always impinges on each light receiving portion in a range of predetermined angles and simultaneously is not beyond each light receiving portion. The calculation of angle is made on the basis of the difference between quantities of light detected by the light receiving portions or the ratio of the difference between quantities of light to the sum of quantities of light, for example, in case where the difference between quantities of light is normalized. It has been found out that with the two-division or four-division photodetector, the difference between quantities of light or the ratio of the difference between quantities of light to the sum of quantities of light is directly proportional to the incident angle. Therefore, the angle can be calculated from the above-mentioned proportional relation.
As mentioned above, the angle detecting device utilizing the two-division or four-division photodetector is not required to use the lens and is less expensive than that utilizing the PSD. However, since the aperture should be set so that the incident light always impinges on each light receiving portion and simultaneously is not beyond each receiving portion, the diameter of the light spot (in case where the aperture is circular) falling on the light receiving portions should be relatively large in order to gain sufficient quantity of light. Consequently, the photodetector which has a large area of light receiving portions should be used. For example, in case of the two-division photodetector, the photodetector area which is approximately two times aperture area is necessary and in case of the four-division photodetector, the photodetector area which is approximately four times aperture area is necessary. The photodetector which has a large area of light receiving portion is of course expensive.